JP4658578B2 - Nozzle ELID grinding method and apparatus - Google Patents

Description

  The present invention relates to electrolytic in-process dressing grinding, and more particularly to a nozzle-type ELID grinding method and apparatus that does not use a grindstone counter electrode.

  With the development of science and technology in recent years, the demand for ultra-precision machining has been remarkably advanced. As a mirror surface grinding means that satisfies this requirement, an electrolytic in-process dressing grinding method (Electrolytic In-process Dressing Method: hereinafter) "ELID grinding method" has been developed and published by the present applicants etc. (RIKEN symposium "latest technology trend of mirror grinding", held on March 5, 1991).

  In this ELID grinding method, as schematically shown in FIG. 8, a conductive grindstone 54 is used instead of the electrode in the conventional electrolytic grinding, and the electrode 52 (hereinafter referred to as a gap) is opposed to the grindstone with a gap (gap). (Referred to as “grinding stone counter electrode”), a conductive liquid 53 is allowed to flow between the grindstone and the electrode, a voltage is applied between the grindstone 54 and the electrode 52, and the grindstone is dressed by electrolysis. Is for grinding. That is, by using the metal bond grindstone 54 as an anode and the electrode 52 opposed to the grindstone surface with a gap as a cathode, and performing electrolytic dressing of the grindstone simultaneously with the grinding operation, the grinding performance can be maintained and stabilized. Is the law. In this figure, 51 is a work (material to be ground), 55 is an ELID power source, 56 is a power feeder, and 57 is a nozzle for conductive liquid.

  In this ELID grinding method, even if the abrasive grains are made fine, clogging of the grinding stone does not occur due to the abrasive grains being sharpened by electrolytic dressing. By making the abrasive grains fine, an extremely excellent processed surface such as a mirror surface is obtained by grinding. be able to. Therefore, the ELID grinding method can maintain the sharpness of the grindstone from high-efficiency grinding to mirror surface grinding, and can be used for various grinding processes as a means to create a high-precision surface that was impossible with the prior art in a short time. Is proposed (for example, Patent Documents 1 and 2).

  As shown in FIG. 9, the “electrolytic dressing control method and apparatus” of Patent Document 1 is configured such that a conductive liquid is allowed to flow between a grindstone 62 and an electrode 63 by a nozzle 64 while a grindstone and an electrode are fed by a power source 65 and a power supply 66. In the electrolytic dressing grinding in which the workpiece 61 is ground while dressing the grindstone by electrolysis, the position control device 67 detects the current or voltage between the electrode and the grindstone, and the detected value falls within the set range. Thus, the distance between the grindstone and the electrode is adjusted by the electrode moving device 68.

  As shown in FIG. 10, the “ELID grinding apparatus for fine shape processing” of Patent Document 2 is provided close to the outer peripheral surface of the conductive grindstone 72, the XY table, and the grindstone, and is centered on the Z axis. An electrolysis electrode 76 that can freely rotate and an electrode guide device 78 are provided. The electrode guide device 78 includes two contacts whose one end is fixed to the electrode 76 for electrolysis. Each contact extends in a diametrical direction centering on the Z axis at a distance from the grindstone and the workpiece. Is partly held at intervals.

Japanese Patent Laid-Open No. 7-1333, “Electrolytic Dressing Control Method and Apparatus” Japanese Patent Application Laid-Open No. 2002-1657, “ELID grinding apparatus for fine shape processing”

As described above, in the conventional ELID grinding method, an electrode ("grinding stone counter electrode") that faces the outer peripheral portion of the grindstone with a slight gap is indispensable.
However, for example, if the diameter of the grindstone is reduced to about 1 to 2 mm, it is difficult or impossible to reduce the size of the electrode and its installation means, and there is a problem that the size reduction of the apparatus is restricted. For this reason, there has been a problem that it is difficult to apply the ELID grinding method in the processing of microlenses and molds for microlenses, for which needs are increasing in recent years.

  The present invention has been made to solve such problems. That is, the object of the present invention is to perform ELID grinding without using a grindstone counter electrode, which has been considered to be indispensable in the past. It is to provide a grinding method and apparatus.

According to the present invention, a nozzle body having a flow path for supplying an electrolytic medium to the surface of a conductive grindstone, a nozzle electrode pair disposed opposite to the flow path, and the nozzle electrode pair for ionization An electrolytic medium containing hydroxide ions (OH ⁻ ) is supplied to the surface of a rotating conductive grinding wheel from an ion supply nozzle consisting of a nozzle power source that applies voltage, and the workpiece is ground while dressing the grinding stone surface by electrolysis or chemical reaction. And
Furthermore, there is provided a nozzle type ELID grinding method characterized by applying a conductive grindstone having a contact surface with a workpiece to a positive potential (+) .
The electrolytic medium is an alkaline aqueous solution or a mist thereof.

Further, according to the present invention, the grindstone includes a rotating conductive grindstone having a contact surface with the workpiece, and an ion supply nozzle for supplying an electrolytic medium containing hydroxide ions (OH ⁻ ) to the surface of the conductive grindstone. Grind the workpiece while dressing the surface by electrolysis or chemical reaction,
The ion supply nozzle includes a nozzle body having a flow path for supplying the electrolytic medium to the surface of the conductive grindstone, a nozzle electrode pair disposed opposite to the flow path, and ionizing the nozzle electrode pair. Ri Do from the nozzle power source for applying a use voltage,
Furthermore, there is provided a nozzle type ELID grinding apparatus comprising a grindstone power source for applying a conductive grindstone to a positive potential (+) .

According to the method and apparatus of the present invention, an ion supply nozzle is provided, and an electrolytic medium (an alkaline aqueous solution or a mist thereof) containing hydroxide ions (OH ⁻ ) is supplied to the surface of the conductive grindstone. Sexual components are attracted to OH ⁻ ions and actively react and elute.
Therefore, even when the tip of the ion supply nozzle is sufficiently separated from the surface of the grindstone, the surface of the grindstone is eluted by electrolysis or chemical reaction, and the surface is oxidized to be non-conductive, so that the electrolytic dressing (ELID) of the grindstone is It becomes possible.
According to the present invention, it is possible to cope with the downsizing of the grindstone, and since the outer peripheral portion of the grindstone is released by setting the electrode installation location as the nozzle tip, the entire grindstone can be used for processing along with the downsizing of the grindstone.
Therefore, ELID grinding can be performed without using the grindstone counter electrode, which has been considered to be indispensable in the past, so that even if the diameter of the grindstone is reduced, for example, ELID grinding can be easily performed.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. In addition, the same code | symbol is attached | subjected to the common part in each figure, and the overlapping description is abbreviate | omitted.

  FIG. 1 is a diagram showing a first embodiment of a nozzle-type ELID grinding apparatus according to the present invention. As shown in this figure, the nozzle-type ELID grinding apparatus 10 of the present invention includes a conductive grindstone 12, a grindstone power supply 14, and an ion supply nozzle 16.

The conductive grindstone 12 is composed of non-conductive abrasive grains (for example, diamond abrasive grains) and conductive bond portions (for example, metals such as cast iron, copper, bronze, Co, and Ni, carbon, etc.), and is electrically conductive as a whole. It is possible to make the abrasive grains stand out (dressing) by electrolyzing the bond portion. The conductive grindstone 12 has a contact surface 12 a with the workpiece 1.
The workpiece 1 may be a non-conductive material (glass, ceramics, etc.) or a conductive material (for example, metal material, semiconductor). When the work 1 is a conductive material, the work 1 is electrically insulated and is configured to have the same potential as the conductive grindstone 12.
The grindstone power source 14 includes a power feed line 15 that feeds power to the conductive grindstone 12, and applies the conductive grindstone 12 to a positive potential (+) from the + terminal 14 a via the power feed line 15. The positive potential (+) is preferably a direct-current pulse voltage, but may be a constant voltage.
In this example, the cathode (-terminal 14b) of the grindstone power supply 14 is grounded. Instead of grounding, a nozzle (-terminal) of a nozzle power source 19 to be described later may be connected.

FIG. 2 is a configuration diagram of the ion supply nozzle of FIG. In this figure, an ion supply nozzle 16 has a function of supplying an electrolytic medium containing hydroxide ions (OH ⁻⁻ ) to the surface of the conductive grindstone 12, and has at least one pair of nozzle main bodies 17 having flow paths 17 a. A nozzle electrode pair 18a, 18b and a nozzle power source 19 are provided.
The electrolytic medium is preferably an alkaline aqueous solution having conductivity or a mist thereof.

The nozzle body 17 supplies the electrolytic medium 2 (liquid or mist) to the surface of the conductive grindstone 12 via the flow path 17a. The nozzle electrode pairs 18a and 18b are electrically insulated from the nozzle body 17 and are disposed facing each other in the flow path 17a. The nozzle power source 19 applies an ionization voltage to the nozzle electrode pairs 18a and 18b. The ionization voltage is preferably a direct-current pulse voltage, but may be a constant voltage or an alternating current.
In this example, the nozzle electrode pairs 18a and 18b are orthogonal to the flow path 17a and face each other so that the distance between the electrodes gradually decreases. The material of the nozzle electrode may be a conductive material such as metal, but a metal having excellent corrosion resistance is desirable.

FIG. 3 is another configuration diagram of the ion supply nozzle. In this example, the nozzle electrode pairs 18a and 18b are ring electrodes arranged along the flow path in the nozzle. The ion supply nozzle 16 ejects hydroxide ions (OH ⁻ ) together with the electrolytic medium 2 (for example, grinding fluid or mist) to the grindstone surface.
The arrangement of the electrodes is not limited to these, and may be arranged in parallel so as to be orthogonal to the flow path, or may have other configurations. Further, in this figure, the conductive grindstone 12 is a disc-shaped grindstone that rotates about the axis Z, but the grindstone surface of the present invention is not limited to this, and is a flat plate, arc surface, or other shape. There may be.

In FIG. 1, the nozzle type ELID grinding apparatus 10 of the present invention further includes a grinding fluid supply nozzle 20. The grinding liquid supply nozzle 20 does not include the nozzle electrode pairs 18 a and 18 b and the nozzle power source 19, and supplies the grinding liquid to the vicinity of the contact portion with the workpiece 1 on the surface of the conductive grindstone 12.
By providing the grinding fluid supply nozzle 20, the electrolytic medium 2 is washed away from the surface of the conductive grindstone 12, and when the work 1 is a conductive material, the work 1 due to hydroxide ions (OH ⁻ ) remaining in the electrolytic medium 2. Corrosion can be reduced. Of course, the lubrication and cooling effect for smooth grinding action is also exhibited.

FIG. 4 is a second embodiment of the nozzle-type ELID grinding apparatus of the present invention. In this example, the workpiece 1 has a spherical shape, and its lower end rotates with an axis that rotates about the Z axis. The conductive grindstone 12 has a small cylindrical shape with a diameter of 5 mm, rotates about the Y axis, and is numerically controlled in the XZ plane.
In this example, the grindstone power supply 14 and the nozzle power supply 19 are integrated to form a single ELID power supply 21.

FIG. 5A is a diagram showing a third embodiment of the nozzle-type ELID grinding apparatus of the present invention. In this example, the workpiece 1 is a dimple mirror having a hemispherical convex portion 1b at the bottom of a cylindrical concave portion 1a. The diameter of the cylindrical concave portion 1a of the dimple mirror is 2 to 3 mm, and the diameter of the hemispherical convex portion 1b is about 1 mm. In addition, the conductive grindstone 12 has a cylindrical shape with a spherical end with a diameter of 100 μm, rotates around the Z axis, and numerically controls the three axes XYZ so that the outer surface of the hemispherical convex portion is a mirror surface. To process.
In this example, the grindstone power source 14 and the nozzle power source 19 are not shown, but are the same as those in the first embodiment diagram or the second embodiment diagram.
In this processing, the processing path of the lower end portion of the conductive grindstone 12 is a contour processing processing path as shown in FIG. 5B, a scanning processing processing path as shown in FIG. Thus, any of the processing paths of spiral processing may be used.

FIG. 6A is a diagram of a fourth embodiment of the nozzle-type ELID grinding apparatus of the present invention. In this example, the workpiece 1 is a mold, an optical element (for example, a Fresnel lens) or the like, and the conductive grindstone 12 is a double V grindstone. The same applies to the single V grindstone. Furthermore, the present invention can also be applied to a general-purpose grindstone having a plurality of V-shaped cross-sectional shapes in which the Fresnel lens cross-section is integrated.
In the case of the conventional electrode type, there is a problem that the grinding liquid and electrolysis are inevitably concentrated between the electrode and the tip of the grindstone, and the shape is lost during electrolytic dressing even if the truing is performed at an angle or sharpness.
However, the present invention can solve such a problem. That is, dressing can be performed on a grindstone whose edge is sharply trued without losing sharpness.

FIG. 6B is a fifth embodiment of the nozzle-type ELID grinding apparatus of the present invention. In this example, the workpiece 1 is a mold or various structural parts, and the conductive grindstone 12 is, for example, a total grindstone. An all-purpose grindstone combining a section having such a curved surface and a V-shaped section may be used.
FIG. 6C is a sixth embodiment of the nozzle-type ELID grinding apparatus of the present invention. In this example, the workpiece 1 is a mold, an optical element (diffraction grating) or the like.
6 (A) and 6 (B), the arrows indicate the grinding liquid ejection direction of the nozzle ELID.
6 (A) and 6 (B), there is an effect that an appropriate dressing can be realized while maintaining the shape for a grindstone having a sharp edge or a specific shape.

FIG. 7 is a seventh embodiment of the nozzle type ELID grinding apparatus of the present invention. In this example, the conductive grindstone 12 is a thin grindstone used for cutting and fine grooving.
In the case of a thin grindstone, in the case of the conventional electrode type, there is a problem that it is difficult to manufacture an electrode having a narrow gap between the grindstones, and it is difficult to adjust the gap with the electrode.
By applying the nozzle type ELID grinding of the present invention, an appropriate and simple dressing can be realized.

Using the apparatus shown in FIG. 1, ELID grinding using a conventional grindstone counter electrode and nozzle type ELID grinding of the present invention were performed.
Table 1 shows the used whetstone, work material, and electrolytic medium, and Table 2 shows the processing conditions. The nozzle-type ELID grinding of the present invention uses a grindstone power supply and a nozzle power supply in combination, and in the conventional ELID grinding, the grindstone power supply is applied between the grindstone counter electrode and the grindstone. Other conditions are the same.

Table 3 is a comparison table of the surface roughness and grinding efficiency ratio obtained in this example. In this table, the grinding ratio indicates the ratio of the processing speed to grinding without applying ELID grinding.
From this table, it was confirmed that a smooth surface roughness close to a mirror surface comparable to conventional ELID grinding can be obtained by the present invention. Further, it was confirmed that the grinding ratio is higher than that of the case where ELID grinding is not applied, although it does not reach the conventional ELID grinding.
When ELID grinding was not applied, when machining was performed under the same conditions, the machining resistance increased rapidly at about 1/3 of the total depth of cut of 90 μm, and spindle overload abnormality occurred. On the other hand, in the nozzle type ELID grinding of the present invention, it was confirmed that low machining resistance was maintained up to the final stage, and the grinding could be performed without crushing or clogging of the grindstone.

Using the apparatus shown in FIG. 4, using a conductive grindstone 12 having a diameter of 5 mm, a spherical surface having a diameter of about 30 mm was processed with a # 2000 grindstone.
As a result, an extremely excellent mirror surface with roughness in the direction parallel to the grinding direction: Ra 0.18 μm, Ry 1.0 μm and roughness in the direction perpendicular to the grinding direction: Ra 0.16 μm, Ry 0.9 μm was obtained. Furthermore, a fine grindstone can also be applied.

As described above, in the nozzle-type ELID grinding method and apparatus of the present invention, a nozzle electrode pair that is a pair of (+) and (−) is formed at the tip of the grinding fluid nozzle, and electrolysis of water in the grinding fluid is performed. OH ^- ions supplied to the grinding wheel surface.
At that time, the potential of the grindstone (+) - When (() as viewed from the electrode relatively (+) as a potential) gives the conductive component of the conductive grindstone is OH ^- tries to actively react attracted to the ion elution Thus, dressing (ELID) of a grindstone becomes possible by making it non-conductive along with (+) ionization.
Therefore, according to the present invention, it is possible to cope with the reduction in the size of the grindstone, and since the outer peripheral portion of the grindstone is released by setting the electrode installation location as the nozzle tip, it is possible to perform processing using the entire circumference of the grindstone with the downsizing of the grindstone.

Further, it is desirable that a (+) potential is applied to the grindstone, but this is not always necessary. That is, since an alkaline aqueous solution is used for the grinding fluid, the metal component of the metal bond grindstone is in an atmosphere that easily elutes as cations in the alkaline aqueous solution, and in such an environment, by supplying OH- ions, The following reactions with metal ions on the surface of the wheel can occur.
M + nOH ⁻ → M (OH) n + ne ⁻ (1)
Here, M is a conductive component (metal or the like) of the grindstone, and OH ⁻ is
_{^{H 2 O → H + + OH}} - ··· (2) ( electrolysis of water) is generated and supply by.
Of course, being able to control the potential of the grindstone is desirable for controlling the dressing amount, but it is not always necessary.

  In addition, this invention is not limited to the Example and embodiment mentioned above, Of course, it can change variously in the range which does not deviate from the summary of this invention.

It is 1st Embodiment figure of the nozzle-type ELID grinding apparatus of this invention. It is a block diagram of the ion supply nozzle of FIG. It is another block diagram of an ion supply nozzle. It is 2nd Embodiment figure of the nozzle type ELID grinding apparatus of this invention. It is 3rd Embodiment figure of the nozzle type ELID grinding apparatus of this invention. It is 4th-6th embodiment figure of the nozzle type ELID grinding apparatus of this invention. It is a 7th embodiment figure of a nozzle type ELID grinding device of the present invention. It is a schematic diagram of the conventional ELID grinding method. 1 is a configuration diagram of “electrolytic dressing control method and apparatus” of Patent Document 1. FIG. 1 is a configuration diagram of an “ELID grinding apparatus for fine shape processing” in Patent Document 2.

Explanation of symbols

1 work, 2 electrolytic medium (liquid or mist),
10 Nozzle type ELID grinding machine,
12 conductive grinding wheel, 12a contact surface,
14 grinding wheel power supply, 14b-terminal, 15 power supply line,
16 ion supply nozzle, 17 nozzle body, 17a flow path,
18a, 18b nozzle electrode pair, 19 nozzle power supply,
20 Grinding fluid supply nozzle, 21 ELID power supply

Claims (5)

Nozzle body having a flow path for supplying an electrolytic medium to the surface of a conductive grindstone, a pair of nozzle electrodes disposed in the flow path, and a nozzle power supply for applying an ionization voltage to the nozzle electrode pair An electrolytic medium containing hydroxide ions (OH ⁻ ) is supplied to the surface of the rotating conductive grindstone from an ion supply nozzle consisting of: and the workpiece is ground while dressing the grindstone surface by electrolysis or chemical reaction ,
Furthermore, the electroconductive grindstone which has a contact surface with a workpiece | work is applied to positive electric potential (+), The nozzle type ELID grinding method characterized by the above-mentioned. The nozzle type ELID grinding method according to claim 1 , wherein the electrolytic medium is an alkaline aqueous solution or a mist thereof. Distance between the electrodes, nozzle type ELID grinding method according to claim 1 or 2 gradually decreases, it is characterized as it shifts to the downstream side of the flow path. A conductive grindstone that rotates has a contact surface with the workpiece surface hydroxyl ions of the conductive grindstone (OH ^-) and a ion supply nozzle for supplying an electrolytic medium comprising, by electrolytic or chemical reactions grindstone surface Grind the workpiece while dressing,
The ion supply nozzle includes a nozzle body having a flow path for supplying the electrolytic medium to the surface of the conductive grindstone, a nozzle electrode pair disposed opposite to the flow path, and ionizing the nozzle electrode pair. Ri Do from the nozzle power source for applying a use voltage,
Furthermore, a nozzle-type ELID grinding apparatus comprising a grindstone power source for applying a conductive grindstone to a positive potential (+) . The nozzle-type ELID grinding apparatus according to claim 4 , wherein the interval between the electrodes gradually decreases as it moves to the downstream side of the flow path.

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